Maybe they aren't to blame.
For awhile now, the error log has only been giving me errors related to that particular caste, and it was always when I went into the Create New World option. I finally got all the errors to stop showing up(although it means I only have hair on the top of the ears and tail, though it's not like you can tell) and DF still crashed when I genned a world. Then I deleted the caste entirely, like I did before(at least from the DF raws, I'm not gonna delete all my hard work in frustration just like that), and the world crashed again both times I tried to generate it. Last time, it worked for me. So now I have to try and figure out what's different.
The most likely suspect right now is the entity files. The must serious change right now is that there is no PLAINS civ in the entity_default file. However, I've also made a few other minor changes to it, such as adding buildings and reactions to dwarves. Actually, I think those are the only 2 changes I've made to the default file. The entity file for my personal humans might be the source instead though. I don't know what could be causing this, and I'd like to test what I've already made before I move on to the recipes stage.
Time for science.
Science has succeeded?
[CASTE:FEMALE]
[FEMALE]
[MULTIPLE_LITTER_RARE]
[CASTE:MALE]
[MALE]
[BODY_DETAIL_PLAN:FACIAL_HAIR_TISSUE_LAYERS]
[CASTE:GENIUS_ART_FEMALE]
[FEMALE]
[MULTIPLE_LITTER_RARE]
[CASTE:GENIUS_ART_MALE]
[MALE]
[BODY_DETAIL_PLAN:FACIAL_HAIR_TISSUE_LAYERS]
[CASTE:_GENIUS_MILITARY_FEMALE]
[FEMALE]
[MULTIPLE_LITTER_RARE]
[CASTE:GENIUS_MILITARY_MALE]
[MALE]
[BODY_DETAIL_PLAN:FACIAL_HAIR_TISSUE_LAYERS]
[CASTE:_GENIUS_LEADER_FEMALE]
[FEMALE]
[MULTIPLE_LITTER_RARE]
[CASTE:GENIUS_LEADER_MALE]
[MALE]
[BODY_DETAIL_PLAN:FACIAL_HAIR_TISSUE_LAYERS]
[SELECT_CASTE:ALL]
All my castes, and the opening tag for the section that describes physical characteristics. The game gens a world fine with it written like this.
[SELECT_CASTE:FEMALE]
[SELECT_ADDITIONAL_CASTE:MALE]
[SELECT_ADDITIONAL_CASTE:GENIUS_ART_FEMALE]
[SELECT_ADDITIONAL_CASTE:GENIUS_ART_MALE]
[SELECT_ADDITIONAL_CASTE:GENIUS_MILITARY_MALE]
[SELECT_ADDITIONAL_CASTE:GENIUS_MILITARY_FEMALE]
[SELECT_ADDITIONAL_CASTE:GENIUS_LEADER_MALE]
[SELECT_ADDITIONAL_CASTE:GENIUS_LEADER_FEMALE]
The old method I used to select castes. I'm guessing I wrote it wrong or something. The reason it's like this is because this is how I got around the duplicate bodyparts issue, though it's not as elegant as only adding the necessary parts to catgirls. Essentially the file declares the body for all normal humans, then it declares it specifically for catgirls.
The process I used to narrow it down:
First, I deleted the catgirl caste and references. Worldgen crashed. Then I reset the default entity and deleted the custom one. Worldgen worked. Then I set the PLAINS entity to use HUMAN_PLAYER, the creature class that this is all a part of. Worldgen crashed. Then I switched all that select_caste nonsense to just [SELECT_CASTE:ALL] and worldgen worked fine, or at least didn't crash.
I'm only posting sections in order to save space, if you want the whole thing, I can post either creature file.